Hey i posted a couple weeks ago about what i thought was diatoms. Everytime i vac the top layer of sand and add new within days it has gone to what i can only describe as "crusty" I have Rio 180, medium level of plants, 2 filters a tetratec ex700 and a eheim 2213 to boost flow. I dose easy carbo and TPN at regular levels and change 25% of the water every week. The fish load is 6 baby angels and 10 adult cardinals. I am in the process of buying equipment to go High Tec co2 and am going to replace all the plants as the current ones were just for algae control in tghe knew tank. I am also getting what appears to be staghorn on the valls and java fern. Any Ideas?